Environmental Degradation in the Drylands of China: Potential Impacts and Possible Remediation Measures: A Review

ENVIRONMENTAL DEGRADATION IN THE DRYLANDS OF CHINA: POTENTIAL IMPACTS AND POSSIBLE REMEDIATION MEASURES: A REVIEW

S. Usman1

1 Natural Resource Institute, Plant Health and Environmental Group, University of Greenwich, Chatham Maritime, Central Avenue Kent UK ME4 4TB

ABSTRACT

China is one of the most affected countries in the world in terms of extent and economic impact of environmental degradation. Desertification is the most severe environmental land degradation problems facing China, commonly caused by wind erosion. Wind erosion occurs widely in arid, semiarid and dry sub-humid zones of northern China, where precipitation is rare and vegetation is sparse. In China desertified land covers an area of 3.3 million km2, accounting for 34% of the total land territory or 79% of the entire arid lands in China. Annual direct economic loss caused by desertification is approximately $6,500,000,000. The best way to control this problem in China are: (1) rehabilitation of tree plantation for complete desertification control, (2) improvement of the economic development system through: (i) economize in the use of resources; (ii) moderate exploitation of the resources; and (iii) environmental protection; and (3) providing measures that should be suited to local conditions such as irrigation system and forage farming system.

INTRODUCTION

Environmental problem such as land degradation inform of desertification is widely recognised as a serious problem and its environmental consequences will remain an important issue of global concern (Eswaran, et al., 2001; Lal, et al., 2003). It is a major threat to agricultural sustainability because it decreases actual and potential soil productivity (Lal, 1998). China is among the most affected countries in the world in term of the extent, intensity and economic impact of environmental degradation, particularly soil erosions and desertification (Zhang et al., 2006). However, an estimate suggests that over 40% of the land area in China (3-4 million km2) is adversely affected by wind and water erosion, loss of grazing, deforestation and salinization leading to land desertification (Berry, 2003). Thus, the problem can be considered as one of the most typical environmental degradation in China. By estimate (COC, 2006), the area affected by desertification is 4.38 million km2, which is equal to 45% of China’s land territory; far exceeds the nation’s total farmland. According to Shi et al. (2007), the problem is more severe in arid, semi-arid and dry grassland areas of China.

Research (Cai and Zhu, 2006) has shown that landform, soil type, vegetation, precipitation, water quality, land reclamation, cultivation, town development, population increase, life style, and land management policy all have close relations with land degradation in China. It has been recognized that soils have ability to restore their fertility after disturbance to a new state under a given set of favourable ecological and land use conditions (Blum, 1994; Zhao, 1995; Lal, 1997). Consequently, improving the productive capacity of degraded soils in such regions of China is particularly important to sustainable agricultural development in term of productivity of soil, food, livestock, water quality and other related land resources such as forestry (World Bank, 2001).

The aim of this paper was to briefly discuss some major environmental degradation in China, focussing primarily on potential impact and some possible remediation measures.

Geography of the study area

China is a large country and the world’s largest population of about 1.3 billion (20 percent of the Earth’s population) occupying most of East Asia (Berry, 2003). The geography of China is highly adverse, with hills, plains and rivers in the east; and deserts, high plateaus and mountain in the west (National Geographic Magazine, 2007). Climate also varied ranging from tropical in the south (Hainan) to sub-arctic in north-eastern (Mangolia) (National Geographic Magazine, 2007).

China has an area of about 9.5 million km2 (Robert, 1999) but only 1.3 million km2 is suitable for cultivation, (i.e. 14% of the total land area). For the remaining, 24% and 28% are grassland and woodland/forest respectively (Berry, 2003). The rest of the areas are unproductive or urban. These unproductive areas are mostly affected by land degradation, which has caused potential reduction of agricultural productivity in China as reported by Huang (2000).

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Figure 1: Map of China (National Geographic Magazine, 2007)

Extent of land degradation in China

China is among the most affected countries in the world (Figure 2) in terms of the extent and economic impact of land degradation (Zhang et al., 2006). One of the consequences of this degradation appears to be in the increase of frequency of severe dust storms in Beijing, which increased from 0.5 in the 1950’s to 2.3 in the 1990’s (China daily, 2002; Berry, 2003). However in year 2002, the two storms (about 56,000 tons) of sand and dust were also deposited in the capital (China Daily, 2002).

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Figure 2: ASSOD Soil Degradation Assessment: Physical Deterioration in China (Van Lynden, G.W.J. and Oldeman, L.R. 1997).

Most of the environmental problems in China as clearly mentioned could have been increased year after year possibly due to human induces activities of cutting down forest vegetation (Van Lynden and Oldeman, 1997). For example, Yunlong (1990) reported that more than 67 million hectares of forest in China were destroyed during 1949-81. In line with this report, the annual expansion of deforestation in China from 1980 to 1990 was also documented (Table 1).

Table1: Annual expansion of degraded land in arid and semiarid regions

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Source: ADB/GEF Project document (2002).

Generally, about six prominent land degradation processes were identified in China namely: desertification, salinization, loss of agricultural use, deforestation, grassland degradation and loss of wetland (Zhang et al., 2006). The most serious among the six prominent land degradation processes observed in China are desertification and erosion by wind (Zhu and Chen, 1994; Xu and Liou, 1997; Wang, 2000; Li et al., 2004). The extent of these two environmental problems in China has been accounted (Table 2).

Table 2: Extent of Grassland Degradation in China in 1998

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Source: World Bank. 2001

POTENTIAL IMPACT OF LAND DEGRADATION IN CHINA

Impact of desertification on soil environment

Desertification has been defined as land degradation in arid and semiarid regions, also including partial dry sub-humid regions, resulting from various factors, including climatic variation and human activities (Gad and Abdel, 2000; ICLDD, 2001). Desertification is one of the severe environmental problems facing China (COC, 2006). The problem increased from 1560 km2 per year in the period of 1950-1970 to 2100 km2 per year in 1970-1980 (Hao, 1995). About 11 provinces (207 counties) in China have become desert in 1949-80 period (see Figure 2) (Yunlong, 1990). This is normally driven by wind erosion. This type of soil erosion was considered as one of the principal mechanisms that caused desertification (Okin et al., 2001).

Theoretically and technically, wind erosion is one of the most serious environmental and agricultural problems in many arid and semiarid agricultural regions of the world (Gomes et al., 2003). It could leads to soil quality deterioration, decline in soil fertility, soil structural damage and removal of nutrient-rich surface soil layers (UNEP, 2003). Similarly, in China Su et al (2003) reported that, desertification caused by wind erosion affects crop production by way of deteriorating soil texture, organic matter content, and nutrients availability.

In China desertified land covers an area of 3.3 million km2, accounting for 34% of the total territory or 79% of the entire arid land in China (Chen et al., 1995). Over 100 million ha of grassland, 7.7 million ha of farmland and 0.1 million ha of woodland have been affected by degradation (Sun et al., 1998). Another estimate indicated that, the desert area and the area affected by desertification covered one third of the territory of China and every year, deserts eat up 2460 km2 of land (Fan and Zhao, 2001). The area affected is far exceeding the nation’s total farm land (COC, 2006). Example, investigation (Wang, 2000) shows that, there are 3.9×105km2 of sandy desertified land, distributed mainly in arid and semiarid regions of Inner Mongolia.

Also, Zhu and Wang (1993) reported that desertified sandy land increased by 25,200 km2 for the period from 1975 to 1987 about 40.5% of which was distributed in the semi arid agro-pastoral regions of northern China. The problem is spreading with an annual growth of 10,400 km2, with 400,000,000 population affected (Muhammed et al., 2004). Annual direct economic loss caused by desertification is approximately $6,500,000,000 (UNCCD, 2002).

Impact of soil erosion on crops

China ranks first in the world, with its 1.79 million km2 of land suffering from soil erosion (about 5 billion tons of soil are eroded every year) (Hao, 1995). Research carried out at different areas in China, particularly on erosion (e.g. Su and Zhao, 2003; Li et al., 2003; Zhao et al., 2005) indicated that, the most important soil erosion in the country is erosion by wind. Soil wind erosion has been identified as important process that affects both the surface features and the biological potential of soils (Marticorena et al., 1997). As mentioned earlier, it could lead to loss of fine soil particles (Hennessy and Kies, 1986). Wind erosion occurs widely in arid, semiarid and dry sub-humid zones of northern China, where precipitation is rare and irregular, vegetation is sparse, wind is frequent, and cultivated soils are left to be bare for a relatively long period from harvest of crops in late September to sowing in late April the following year (Zhu and Chen, 1994; Li, 1998).

It is well-known that soil erosion by wind affects the surface soil layers and other important soil components of soil in arid and semiarid areas (Marticorena et al., 1997; Wild, 2003). Wind erosion increased soil coarseness and surface soil deterioration (Su et al., 2002; Gomes et al., 2003). Such deterioration can result in a noticeable decline in organic matter on agricultural fields and finally leads to partial or even complete destruction of soil productivity by reducing porosity and water infiltration rates, damaging soil structure and aggregate stability, as well as storage and availability of nutrients (Kennedy, 1995; Su et al., 2002). These problems of wind erosion have been identified by Lal (1998) as one of the greatest threats to sustainable crop production worldwide.

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